Replacing the EM34 by the 6E5C

In many cases it's possible to replace the rare and expensive eye tube EM34 by the Russian 6E5C (6e5s). (This 6E5C is an octal-base version of the American 6E5 (with UX6 Base)).

The EM34 has two shadow angles with different sensitivity, which requires two triode units inside the bulb with different amplification as control preamps.

Unlike to the EM34, the 6E5C has only one shadow angle, which then requires only a single triode. 

Replacing the EM34 by a 6E5C requires the urgent need of the rewiring of some socket connections, as otherwise the 6E5C will be destroyed and severe damage of the circuit may happen !  

Note the base diagrams of the EM34 and the 6E5C for a proper rewiring.

The 1 MegOhm resistor R1 at pin 3 (a1) will be retained, while the former resistor R2 (at a2) will be dropped.

Replacing the EM34 by the EM84

In many cases it's possible to replace the EM34 magic eye by the magic bar tuning indicator EM84, as the example by the Philips BF510A clearly proofs.

On the left one can see the EM84 without input signal, which demonstrates that nothing of the indication sweep is left.  

The space laterally of the EM84 fluorescent bar should be covered by suitable material and colour. 

The EM34 has two shadow angles with different sensitivity, which requires two triode units inside the bulb with different amplification as control preamps.

Unlike to the EM34, the EM84 has only one moving pattern which then requires only a single triode.

Replacing the EM34 by a EM84 requires the change of the socket with adequate wiring.

Note the base diagrams of the EM34 and the EM84 for a proper rewiring. 

Both the 1 MegOhm resistors R1 and R2 will be dropped and replaced by a new 470...500 kOhm resistor R3. Additionally a jumper between anode triode (aT) and control rod (st) is required (pin 7 to 9).

Don't forget the rewiring of the heater connections.

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If the 6e5s (Cyrillic 6E5C) is too sensitive (close on too weak a signal), as is likely, then put a resistor divider such as 3M3 Ohms in series with grid and 1M Ohm from grid to ground will give about 1/4 sensitivity.

I just replaced an EM34 and at first the tube didn't light at all. The pins of the 1985 NOS tube had tarnished in store, a wipe with a hard "ink" eraser/rubber cured it.

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I used a 6E5C to replace a EM34. I was pleased with the results but the eye was too sensitive.

I will use the 3M3 Ohms in series with the grid.

I think I already have a 1M from grid to ground

Thanks

Don in Scottsdale, AZ

 

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